Transverse spin diffusion and spin rotation in very dilute, spin-polarized sup 3 He- sup 4 He mixtures

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.7510· OSTI ID:5131509

Candela, D; McAllaster, D R; Wei, L ^[1]

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1. Laboratory for Low Temperature Physics, Physics and Astronomy Department, University of Massachusetts at Amherst, Amherst, Massachusetts (USA)

We report measurements of the transverse-spin-diffusion coefficient {ital D}{sub {perpendicular}} and the spin-rotation parameter {Omega}{tau}{sub {perpendicular}} for two very dilute {sup 3}He-{sup 4}He mixtures ({ital x}{sub 3}=1.82{times}10{sup {minus}3} and 6.26{times}10{sup {minus}4}) spin polarized by an 8-T magnetic field. Brute-force spin polarization up to 40% was achieved at the lowest temperature, 6 mK. We find that {Omega}{tau}{sub {perpendicular}} increases monotonically as the temperature is reduced through the Fermi temperature {ital T}{sub {ital F}}, in disagreement with the only previous experiment but in good agreement with recent theory. Unlike the earlier experiment, which measured spin echoes, the present experiments employed a spin-wave technique that avoids nonlinear excitation of the spin field. We compare our results with the recent calculations of Jeon and Mullin for spin transport in dilute gases with arbitrary polarization and degeneracy. The best fit to the data is obtained by scaling the quasiparticle interaction {ital V}({ital q}) proposed by Ebner by a modest factor, 1.07. The corresponding {ital s}-wave scattering length is {ital a}={minus}1.21 A. Good agreement is found for {Omega}{tau}{sub {perpendicular}}({ital T}) at both concentrations and all temperatures, and for {ital D}{sub {perpendicular}}/{Omega}{tau}{sub {perpendicular}}({ital T}) apart from the lower concentration at {ital T}{lt}20 mK. The discrepancy in {ital D}{sub {perpendicular}}/{Omega}{tau}{sub {perpendicular}} at the lowest temperatures and {ital x}{sub 3} could be explained by an unanticipated polarization dependence or by modification of the spin-wave boundary condition by processes occurring at the interface between the mixture and the silica cavity wall.

• OSTI ID: 5131509
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:14; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
HELIUM
SPIN ORIENTATION
DIFFUSION
HELIUM 3
HELIUM 4
ROTATION
ULTRALOW TEMPERATURE
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FLUIDS
GASES
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MOTION
NONMETALS
NUCLEI
ORIENTATION
RARE GASES
STABLE ISOTOPES
640450* - Fluid Physics- Superfluidity